1. Field of the Invention
The present invention relates to a circuit including a MOS transistor, and, more particularly, to control of the drain-source breakdown voltage of a MOS transistor.
2. Description of the Related Art
It is generally known that as the collector-emitter voltage is kept applied to a bipolar transistor having an open base, avalanche breakdown occurs at a certain voltage, causing a large current to flow between the collector and emitter. This is because the dark current between the collector and emitter causes an electron avalanche in the base area. This is described, for example, on pages 231-233 in "Physics and Technology of Semiconductor Devices" (John Wiley and Sons, Inc. 1976) by A. S. Grove.
Although the aforementioned mechanism for causing the avalanche breakdown is conventionally known, the avalanche breakdown voltage depends on the manufacturing process of semiconductor devices, such as the impurity concentration of the base, and cannot be changed once the device manufacturing process is determined.